(1) Field of the Invention
This invention relates to pesticidal sheets, containers or the like and to methods of manufacturing same.
(2) Description of the Prior Art
There are two main methods for applying pesticidal protection to a surface or area. The first method is to apply the pesticide to the surface by mixing it with a liquid carrier, spraying the mixture onto the surface and allowing the liquid carrier to evaporate, leaving the pesticide as a residue. The pests come into contact with the pesticide and die. These pesticides have an effective life of approximately 3 months. However, their effectiveness can be markedly reduced if the surface is washed or becomes damp, removing the pesticide. Because of the nature of spraying the pesticide onto the surface, a uniform distribution of pesticide cannot be assured and so a relative high toxicity level must be used to ensure effectiveness. Even then, areas of the surface may be missed, allowing the pests to pass through a target zone without coming into contact with the pesticide.
The second method is to employ pest strips which contain a vaporizing pesticide which must diffuse throughout the area to be protected. Again, as the pesticide must be effective throughout the whole area, fairly high toxicity levels must be used. As the pesticide must be able to vapourize, it is generally unstable and means must be provided to control the breakdown of the pesticide or the effective life of the strip would only be from a few hours to e.g. 7-10 days.
For example, Australian Pat. No. 491714 (Herculite Protective Fabrics Corporation) discloses a pesticidal strip where a pesticidal impregnated sheet is enclosed in a nonporous container which allows a controlled migration of the pesticide to the surface of the container. The patent states it is essential to use this form of encapsulation as the pesticides are subject to rapid breakdown (or decomposition) at 100.degree. F. and gives examples of pesticides which have effective lives in open atmosphere, of approximately 7-10 days but which may be effective for up to 90 days using the encapsulation method. Should the container be damaged, the pesticides would rapidly lose their effectivness and the user would be exposed to very high toxicity levels with detremental health effects. The pesticides employed rely on their vapourising characteristics, and leave little, if any, residue.